Adding SLF4j to satisfy required depdency in GAE env

git-svn-id: https://svn.apache.org/repos/asf/incubator/photark/trunk@1004120 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/photark-appengine-webapp/pom.xml b/photark-appengine-webapp/pom.xml
index 034d1c5..93c5ada 100644
--- a/photark-appengine-webapp/pom.xml
+++ b/photark-appengine-webapp/pom.xml
@@ -113,6 +113,12 @@
 			</exclusions>
 		</dependency>
 
+        <dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-api</artifactId>
+			<version>1.6.0</version>
+        </dependency>
+
 		<dependency>
 		   <groupId>org.dojotoolkit</groupId>
 		   <artifactId>dojo</artifactId>